https://devzone.nordicsemi.com/f/nordic-q-a/11139/why-bootloader-in-sdk9-addr-0-1In bootloader of sdk9 I find ble_gap_addr_t addr; err_code = sd_ble_gap_address_get(&amp;addr); APP_ERROR_CHECK(err_code); // Increase the BLE address by one when advertising openly. addr.addr[0] += 1; err_code = sd_ble_gap_address_set(BLE_GAP_ADDR_CYCLE_MODE_NONEen-USTelligent Community 13Tue, 05 Jan 2016 13:46:27 GMThttps://devzone.nordicsemi.com/thread/41753?ContentTypeID=1Tue, 05 Jan 2016 13:46:27 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8e5d8d02-5455-4562-8e56-0a3217585357Anders Strand<p>This code is executed when the dfu bootloader is unable to load stored peer data from flash. This means that it will require a new connection from the smartphone. The smartphone on the other hand, might have stored bond information. It will therefore try to connect to the dfu with the stored encryption keys.</p> <p>By changing its address, the device will appear as a new device to the smartphone. This changing is done in reaction to an error (no peer data), and should not really be removed. You should rather make sure that peer data is stored in your application. See <a href="http://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk51.v9.0.0%2Fbledfu_appbonding.html&amp;cp=4_0_4_4_3_2_3">this</a> page about sharing bond info in the infocenter. <a href="https://devzone.nordicsemi.com/question/37060/dfu-device-address-changes/">This</a> and <a href="https://devzone.nordicsemi.com/question/48962/sd_ble_gap_address_get-returns-different-addr-for-app-and-dfu/">this</a> devzone thread might also be of interest.</p><div style="clear:both;"></div>